You can usually tell if something is rough or smooth when you run your fingers across the surface. But what about things that are too small or too big to go over it? The earth looks smooth out of space, but someone standing at the foot of the Himalayas would not agree. Scientists measure surfaces at different scales to account for different sizes, but these standards are not always consistent.
A recent study by the Swanson School of Engineering at the University of Pittsburgh has measured an ultrananocrystalline diamond coating, which is prized for its hard but smooth properties, and has shown to be far rougher than previously thought. Their findings could help researchers better predict how surface topography affects the surface properties of materials used in various environments, from microsurgery and motors to satellite housings or spacecraft.
"An important measure of the" roughness "of a surface is its average slope is how steep it is," says Tevis Jacobs, Assistant Professor of Mechanical and Material Sciences at Pitt. "We found that the surface of this nanodiamond film looks very different depending on the scale used."
Dr. Jacobs and his team were featured in the American Chemical Society's (ACS) ACS Applied Materials and Interfaces . They performed more than 1
Dr. Jacobs explains, "The nanodiamond surface is so smooth that you can see your reflection in it, and by combining all the measurements, including the smallest scales, we have shown that this" smooth "material has an average inclination of 50 degrees steeper as the Austrian Alps, measured on the basis of a human foot (39 degrees). "
" By electron microscopy, we were able to determine the smallest end of the measurement range, we can not even define the topography below the atomic scale, "says Dr , Jacobs. "If we then combine all the scales, we could eliminate the problem of roughness deviation between scales, and we can calculate true scale-invariant roughness parameters."
"We Knew One Hundred For years surface roughness has governed surface properties, and the missing link is that we could not quantify their effect, for example, biomedical applications have led to different results as to whether roughness promotes or diminishes cell adhesion The roughness across scales will open the door to the solution of this age-old mystery in surface analysis. "
The ultimate goal is to have predictive models of how roughness determines surface properties such as adhesion, friction, or conduction. The breakthrough of Dr. Jacobs is the first step in a steep and very steep struggle to create and validate these models.
"We are currently conducting property measurements on this nanodiamond material and many other surfaces in order to use mechanics models to link topography and properties," he says. "By identifying the scales or combination of scales that matter most to a particular application, we can identify which surface refinement techniques produce the best results, avoiding a costly and time-consuming trial-and-error approach."
Researchers are "rough" with nanomaterials to eliminate problematic stickiness from smooth surfaces
Abhijeet Gujrati et al. Combination of TEM, AFM and profilometry for the quantitative characterization of topography across all scales, Applied Materials and Interfaces of ACS (2018). DOI: 10.1021 / acsami.8b09899